Humoral immune response in lactating dairy cows after repeated exposure to human chorionic gonadotropin

Our objective was to determine if repeated exposure of lactating dairy cows to human chorionic gonadotropin (hCG) would induce an antibody (Ab) response against hCG. Cows either received an hCG injection (hCG; n = 24, each given 2000 IU im) or no treatment (CON; n = 22) 18 days after a timed AI (TAI) and 7 days before initiation of Ovsynch for resynchronization of ovulation and TAI. A subgroup of cows continued in the experiment to receive a second hCG injection (n = 17) 35 days after the first exposure to hCG, whereas another subgroup served as controls (n = 9). Another subgroup of cows continued in the experiment to receive a third hCG injection (n = 11) 35 days after the second exposure to hCG, whereas cows not receiving hCG served as controls (n = 8). A binding radioimmunoassay was used to detect hCG antibodies in serum samples collected 0, 7, 14, 21, and 28 days after treatment. A positive Ab response (>6.2% bound) was defined as three standard deviations above CON binding. No cows had hCG antibodies at Day 0 before the first exposure to hCG. After the first hCG treatment, there was no difference (P = 0.52) between Ab positive cows in CON (0%) and hCG (4%) treatments. At the second hCG treatment, on Day 0 there was no difference (P = 0.65) between CON (0%) and hCG (6%) cows, whereas, more (P = 0.02) hCG cows (47%) were positive than CON cows (0%) within 28 days of the hCG injection. At the third hCG injection, hCG cows tended (P = 0.09) to have a greater percentage of Ab positive (36%) than CON cows (0%), whereas after the injection, a greater (P < 0.01) percentage of hCG cows were positive (hCG = 73% vs. CON = 0%). After the second and third exposure to hCG, 8 of 17 and 8 of 11 cows within the hCG group had greater percent Ab bound at 7, 14, 21, and 28 days after hCG than cows in CON and those with no Ab response. The greatest percent Ab binding occurred at 14 days after the second and third hCG exposure. We concluded that some but not all lactating dairy cows developed an Ab response after repeated exposure to hCG and that maximum response occurred within 14 days after hCG exposure.     

Construction of a recombinant BHV-1 expressing the VP1 gene of foot and mouth disease virus and its immunogenicity in a rabbit model

Foot-and-mouth disease (FMD) and infectious bovine rhinotracheitis (IBR) are two important infectious diseases of cattle. Using bovine herpesvirus type 1 (BHV-1) as a gene delivery vector for development of live-viral vaccines has gained widespread interest. In this study, a recombinant BHV-1 was constructed by inserting the synthetic FMDV (O/China/99) VP1 gene in the the gE locus of BHV-1 genome under the control of immediately early gene promoter of human cytomegalovirus (phIE CMV) and bovine growth hormone polyadenylation (BGH polyA) signal. After homologous recombination and plaque purification, a recombinant virus named BHV-1/gE⁻/VP1 was acquired and identified. The immunogenicity was confirmed in a rabbit model by virus neutralization test and enzyme-linked immunosorbent assay (ELISA). The result indicated that the BHV-1/gE⁻/VP1 has the potential for being developed as a bivalent vaccine for FMD and IBR.     

Doubly robust estimates for binary longitudinal data analysis with missing response and missing covariates

Longitudinal studies often feature incomplete response and covariate data. Likelihood-based methods such as the expectation-maximization algorithm give consistent estimators for model parameters when data are missing at random (MAR) provided that the response model and the missing covariate model are correctly specified; however, we do not need to specify the missing data mechanism. An alternative method is the weighted estimating equation, which gives consistent estimators if the missing data and response models are correctly specified; however, we do not need to specify the distribution of the covariates that have missing values. In this article, we develop a doubly robust estimation method for longitudinal data with missing response and missing covariate when data are MAR. This method is appealing in that it can provide consistent estimators if either the missing data model or the missing covariate model is correctly specified. Simulation studies demonstrate that this method performs well in a variety of situations.     

Intrinsic pKas of ionizable residues in proteins: An explicit solvent calculation for lysozyme

Molecular dynamics simulations of triclinic hen egg white lysozyme in aqueous solution were performed to calculate the intrinsic pK_as of 14 ionizable residues. An all-atom model was used for both solvent and solute, and a single 180 ps simulation in conjunction with a Gaussian fluctuation analysis method was used. An advantage of the Gaussian fluctuation method is that it only requires a single simulation of the system in a reference state to calculate all the pK_as in the protein, in contrast to multiple simulations for the free energy perturbation method. pK_int shifts with respect to reference titratable residues were evaluated and compared to results obtained using a finite difference Poisson-Boltzmann (FDPB) method with a continuum solvent model; overall agreement with the direction of the shifts was generally observed, though the magnitude of the shifts was typically larger with the explicit solvent model. The contribution of the first solvation shell to the total charging free energies of the titratable groups was explicitly evaluated and found to be significant. Dielectric shielding between pairs of titratable groups was examined and found to be smaller than expected. The effect of the approximations used to treat the long-range interactions on the pK_int shifts is discussed. © 1994 Wiley-Liss, Inc.     

How predator functional responses and Allee effects in prey affect the paradox of enrichment and population collapses

In Rosenzweig-MacArthur models of predator-prey dynamics, Allee effects in prey usually destabilize interior equilibria and can suppress or enhance limit cycles typical of the paradox of enrichment. We re-evaluate these conclusions through a complete classification of a wide range of Allee effects in prey and predator's functional response shapes. We show that abrupt and deterministic system collapses not preceded by fluctuating predator-prey dynamics occur for sufficiently steep type III functional responses and strong Allee effects (with unstable lower equilibrium in prey dynamics). This phenomenon arises as type III functional responses greatly reduce cyclic dynamics and strong Allee effects promote deterministic collapses. These collapses occur with decreasing predator mortality and/or increasing susceptibility of the prey to fall below the threshold Allee density (e.g. due to increased carrying capacity or the Allee threshold itself). On the other hand, weak Allee effects (without unstable equilibrium in prey dynamics) enlarge the range of carrying capacities for which the cycles occur if predators exhibit decelerating functional responses. We discuss the results in the light of conservation strategies, eradication of alien species, and successful introduction of biocontrol agents.     

Predation Hot Spots: Large Scale Impact of Local Aggregations

Abstract   Broad scale survey distributions of fish are dominated by some extremely high catches. With a novel survey design we resolved the small-scale fish distribution in the spatio-temporal vicinity of these extreme hauls and showed that in the North Sea they generally do not occur in isolation. An additional case study where stomach contents of fish predators were analyzed revealed that they actually indicate aggregations of piscivorous fish predators on prey aggregations. We show that the predation impact can reach immense dimensions, an aggregation of more than 50 million juvenile cod (Gadus morhua) was entirely wiped out in 5 days by predatory whiting (Merlangius merlangus), aggregating on these juveniles in an area of approximately 18 km². The consumption of only 32 hot spots of similar magnitude as observed in our study adds up to the average size of an incoming North Sea cod year class. These findings support the hypothesis of predation as the major source of mortality in young-of-the-year demersal fish species and questions the generality of fish aggregation as an effective anti-predator strategy. This study highlights the system-wide structuring force of small-scale predation hot spots and further points to the importance of a more realistic implementation of local high-intensity predation events in food web models. Electronic supplementary material:   The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Ecosystem productivity can be predicted from potential relative growth rate and species abundance

We show that ecosystem-specific aboveground net primary productivity (SANPP, g g⁻¹ day⁻¹, productivity on a per gram basis) can be predicted from species-level measures of potential relative growth rate (RGR_max), but only if RGR_max is weighted according to the species' relative abundance. This is in agreement with Grime's mass-ratio hypothesis. Productivity was measured in 12 sites in a French Mediterranean post-agricultural succession, while RGR_max was measured on 26 of the most abundant species from this successional sere, grown hydroponically. RGR_max was only weakly correlated ( r ² = 0.12, P  < 0.05) with field age when species abundance was not considered, but the two variables were strongly correlated ( r ² = 0.81, P  < 0.001) when the relative abundance of species in each field was taken into account. SANPP also decreased significantly with field age. This resulted in a tight relationship ( r ² = 0.77, P  < 0.001) between productivity and RGR_max weighted according to species relative biomass contribution. Our study shows that scaling-up from the potential properties of individual species is possible, and that information on potential and realized species traits can be integrated to predict ecosystem functioning.     

Dose responses of gibberellins

To determine the response type, published data for the most widely used bioassays for gibberellins have been analyzed by means of a computer program for estimating sensitivity parameters, or by interpolation. The dose response data are almost uniformly subsensitive, i. e. more than an 81-fold increase in external gibberellin concentration is required for a change from 10 to 90% of maximal response (S₉₀/S₁₀). Data for the interaction of gibberellins with artificial membranes are, in contrast, markedly ultrasensitive (S₉₀/S₁₀± 10). This difference further strengthens the view that lipid structures do not function as receptors for gibberellins. Most of the subsensitive dose responses for gibberellins can be quite precisely represented by cooperative isotherms. However, available data are insufficiently detailed for an unequivocal choice among cooperative, multiphasic or more complex kinetics.